In some headlamps arranged on the left and right sides of the front portion of a vehicle, a light amount control mechanism for switching the amount of shielding of light emitted from the light source can be provided. Examples of such headlamps may include those described in Japanese Patent Application Laid-Open Nos. 2014-002963, 2014-007048, and 2015-046341.
Such a light amount control mechanism can include a movable shade configured to rotatably switch a shielding amount of light emitted from a light source, and an actuator configured to drive the movable shade. In this light amount control mechanism, for example, the movable shade is controlled to rotate to a first position, so that the irradiation mode is switched to a low beam irradiation mode for irradiating a short distance with light, and alternatively, the movable shade is controlled to rotate to a second position, so that the irradiation mode is switched to a high beam irradiation mode for irradiating a long distance with light. Hereinafter, one example of such a conventional light amount control mechanism will be described below with reference to FIGS. 1 and 2A and 2B.
FIG. 1 is a front cross-sectional view of a conventional light amount control mechanism, and FIGS. 2A and 2B are each an enlarged detailed view of a part F of FIG. 1. As illustrated in FIG. 1, a vehicle headlamp is provided with a reflector 108 for reflecting light emitted from a light source (not illustrated) toward the front of the vehicle, and a light amount control mechanism 101 for switching a shielding amount of light reflected by the reflector 108.
In the light amount control mechanism 101, a movable shade 102 is rotatably supported by a housing 106 by a rotary shaft 105 together with a bracket 104. More specifically, the rotatable rotary shaft 105 is inserted through and held in the housing 106 in the width direction (left-right direction in FIGS. 1 and 2A and 2B), and the movable shade 102 and the bracket 104 are coupled to the rotary shaft 105.
The movable shade 102 is housed in the housing 106 and driven by an actuator (not illustrated), such as a solenoid, so that the irradiation mode is switched to the low beam irradiation mode or the high beam irradiation mode by the rotation of the movable shade 102 to move to the first position or the second position.
Incidentally, in the light amount control mechanism 101 illustrated in FIG. 1, the positional precision in the rotation axis direction (width direction) of the movable shade 102 for forming the light distribution is important. However, since the movable shade 102 and the bracket 104 are rotating parts, a predetermined axial gap δ is usually required to be formed between the bracket 104 on the rotating side and the housing 106 on the stationary side as shown in FIG. 2A. When the axial gap δ is formed between the bracket 104 and the housing 106 in this manner, a backlash in the rotational axis direction (left-right direction in the drawings) is generated in the movable shade 102, and a problem arises in that the backlash of the movable shade 102 causes a variation in light distribution.
In order to solve the above-mentioned problem, as illustrated in FIG. 2B, it is conceivable that an axial gap is not provided between the bracket 104 and the housing 106; however, when the axial gap is not provided, another problem arises that the rotation of the movable shade 102 is not smoothly performed particularly when the bracket 104 and the housing 106 are heated and thermally expanded.